/src/git/commit-reach.c

Source
#define USE_THE_REPOSITORY_VARIABLE

#include "git-compat-util.h"
#include "commit.h"
#include "commit-graph.h"
#include "decorate.h"
#include "hex.h"
#include "prio-queue.h"
#include "ref-filter.h"
#include "revision.h"
#include "tag.h"
#include "commit-reach.h"
#include "ewah/ewok.h"
#include "trace2.h"

/* Remember to update object flag allocation in object.h */
#define PARENT1   (1u<<16)
#define PARENT2   (1u<<17)
#define STALE   (1u<<18)
#define RESULT    (1u<<19)
#define ENQUEUED  (1u<<20)

static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT | ENQUEUED);

static int compare_commits_by_gen(const void *_a, const void *_b)
{
  const struct commit *a = *(const struct commit * const *)_a;
  const struct commit *b = *(const struct commit * const *)_b;

  timestamp_t generation_a = commit_graph_generation(a);
  timestamp_t generation_b = commit_graph_generation(b);

  if (generation_a < generation_b)
    return -1;
  if (generation_a > generation_b)
    return 1;
  if (a->date < b->date)
    return -1;
  if (a->date > b->date)
    return 1;
  return 0;
}

/*
 * A prio_queue with O(1) termination check.  'max_nonstale' tracks
 * the lowest-priority non-stale commit enqueued so far; once it is
 * popped, every remaining entry is known to be STALE.
 */
struct nonstale_queue {
  struct prio_queue pq;
  struct commit *max_nonstale;
};

static void nonstale_queue_put(struct nonstale_queue *queue,
             struct commit *c)
{
  struct commit *old = queue->max_nonstale;

  prio_queue_put(&queue->pq, c);
  if (c->object.flags & STALE)
    return;
  if (!old || queue->pq.compare(old, c, queue->pq.cb_data) <= 0)
    queue->max_nonstale = c;
}

static struct commit *nonstale_queue_get(struct nonstale_queue *queue)
{
  struct commit *commit = prio_queue_get(&queue->pq);

  if (commit == queue->max_nonstale)
    queue->max_nonstale = NULL;

  return commit;
}

static void clear_nonstale_queue(struct nonstale_queue *queue)
{
  clear_prio_queue(&queue->pq);
  queue->max_nonstale = NULL;
}

/*
 * Priority queue with per-side commit counters for paint_down_to_common().
 * Each non-stale queued commit occupies exactly one bucket: PARENT1-only,
 * PARENT2-only, or both (a pending merge-base candidate).
 */
struct paint_state {
  struct prio_queue queue;
  size_t parent1_count;
  size_t parent2_count;
  size_t mb_candidate_count;
  timestamp_t min_generation;
  timestamp_t last_gen;
  timestamp_t topo_ceiling;
};

static void paint_count_update(struct paint_state *state,
             unsigned flags, int delta)
{
  switch (flags & (PARENT1 | PARENT2 | STALE)) {
  case PARENT1:
    state->parent1_count += delta;
    break;

  case PARENT2:
    state->parent2_count += delta;
    break;

  case PARENT1 | PARENT2:
    state->mb_candidate_count += delta;
    break;

  case PARENT1 | PARENT2 | STALE:
    break;

  default:
    BUG("unexpected paint state");
  }
}

static void paint_queue_put(struct paint_state *state,
          struct commit *c, unsigned add_flags)
{
  unsigned old_flags = c->object.flags;
  c->object.flags |= add_flags;

  if (old_flags & ENQUEUED) {
    paint_count_update(state, old_flags, -1);
    paint_count_update(state, c->object.flags, 1);
  } else {
    c->object.flags |= ENQUEUED;
    prio_queue_put(&state->queue, c);
    paint_count_update(state, c->object.flags, 1);
  }
}

/*
 * Dequeue the next commit for the paint walk, or return NULL when
 * no more merge bases can be discovered.
 */
static struct commit *paint_queue_get(struct paint_state *state)
{
  struct commit *commit = prio_queue_get(&state->queue);
  timestamp_t generation;

  if (!commit)
    return NULL;

  commit->object.flags &= ~ENQUEUED;
  generation = commit_graph_generation(commit);

  if (state->min_generation && generation > state->last_gen)
    BUG("bad generation skip %"PRItime" > %"PRItime" at %s",
        generation, state->last_gen,
        oid_to_hex(&commit->object.oid));
  state->last_gen = generation;

  /* generation cutoff */
  if (generation < state->min_generation)
    return NULL;

  /*
   * Check exit condition before decrementing: the counters
   * still include this commit, so the last non-stale commit
   * sees a non-zero count and is returned for processing.
   */
  if (!state->mb_candidate_count) {
    /* only stale entries remain */
    if (!state->parent1_count && !state->parent2_count)
      return NULL;

    /* one side is exhausted */
    if ((!state->parent1_count || !state->parent2_count) &&
        generation < state->topo_ceiling)
      return NULL;
  }

  paint_count_update(state, commit->object.flags, -1);
  return commit;
}

/*
 * See Documentation/technical/paint-down-to-common.adoc
 *
 * All input commits in one and twos[] must have been parsed!
 */
static int paint_down_to_common(struct repository *r,
        struct commit *one, int n,
        struct commit **twos,
        timestamp_t min_generation,
        enum merge_base_flags mb_flags,
        struct commit_list **result)
{
  /*
   * Generation ordering is required for the side-exhaustion and
   * single-result early exits, which rely on topological traversal
   * order (children visited before parents) in the ordered region.
   */
  struct paint_state state = {
    .queue = { compare_commits_by_gen_then_commit_date }
  };
  struct commit *commit;
  int i;
  int steps = 0;
  struct commit_list **tail = result;

  state.min_generation = min_generation;
  state.last_gen = GENERATION_NUMBER_INFINITY;
  state.topo_ceiling = corrected_commit_dates_enabled(r)
    ? GENERATION_NUMBER_INFINITY
    : GENERATION_NUMBER_V1_MAX;


  one->object.flags |= PARENT1;
  if (!n) {
    commit_list_append(one, result);
    return 0;
  }
  paint_queue_put(&state, one, 0);

  for (i = 0; i < n; i++)
    paint_queue_put(&state, twos[i], PARENT2);

  while ((commit = paint_queue_get(&state))) {
    struct commit_list *parents;
    int flags;
    steps++;

    flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
    if (flags == (PARENT1 | PARENT2)) {
      if (!(commit->object.flags & RESULT)) {
        commit->object.flags |= RESULT;
        tail = commit_list_append(commit, tail);
        /*
         * When the queue is generation-ordered,
         * no remaining common ancestor can be a
         * descendant of this one.
         */
        if (!(mb_flags & MERGE_BASE_FIND_ALL) &&
            state.last_gen < state.topo_ceiling)
          break;
      }
      /* Mark parents of a found merge stale */
      flags |= STALE;
    }
    parents = commit->parents;
    while (parents) {
      struct commit *p = parents->item;
      parents = parents->next;
      if ((p->object.flags & flags) == flags)
        continue;
      if (repo_parse_commit(r, p)) {
        clear_prio_queue(&state.queue);
        commit_list_free(*result);
        *result = NULL;
        /*
         * At this stage, we know that the commit is
         * missing: `repo_parse_commit()` uses
         * `OBJECT_INFO_DIE_IF_CORRUPT` and therefore
         * corrupt commits would already have been
         * dispatched with a `die()`.
         */
        if (mb_flags & MERGE_BASE_IGNORE_MISSING_COMMITS)
          return 0;
        return error(_("could not parse commit %s"),
               oid_to_hex(&p->object.oid));
      }
      paint_queue_put(&state, p, flags);
    }
  }

  clear_prio_queue(&state.queue);
  trace2_data_intmax("paint_down_to_common", r,
         "steps", steps);
  commit_list_sort_by_date(result);
  return 0;
}

static int merge_bases_many(struct repository *r,
          struct commit *one, int n,
          struct commit **twos,
          enum merge_base_flags mb_flags,
          struct commit_list **result)
{
  struct commit_list *list = NULL, **tail = result;
  int i;

  for (i = 0; i < n; i++) {
    if (one == twos[i]) {
      /*
       * We do not mark this even with RESULT so we do not
       * have to clean it up.
       */
      *result = commit_list_insert(one, result);
      return 0;
    }
  }

  if (!one)
    return 0;
  if (repo_parse_commit(r, one))
    return error(_("could not parse commit %s"),
           oid_to_hex(&one->object.oid));
  for (i = 0; i < n; i++) {
    if (!twos[i])
      return 0;
    if (repo_parse_commit(r, twos[i]))
      return error(_("could not parse commit %s"),
             oid_to_hex(&twos[i]->object.oid));
  }

  if (paint_down_to_common(r, one, n, twos, 0, mb_flags, &list)) {
    commit_list_free(list);
    return -1;
  }

  while (list) {
    struct commit *commit = pop_commit(&list);
    if (!(commit->object.flags & STALE))
      tail = commit_list_append(commit, tail);
  }
  commit_list_sort_by_date(result);
  return 0;
}

int get_octopus_merge_bases(struct commit_list *in, struct commit_list **result)
{
  struct commit_list *i, *j, *k;

  if (!in)
    return 0;

  commit_list_insert(in->item, result);

  for (i = in->next; i; i = i->next) {
    struct commit_list *new_commits = NULL, *end = NULL;

    for (j = *result; j; j = j->next) {
      struct commit_list *bases = NULL;
      if (repo_get_merge_bases(the_repository, i->item,
             j->item, &bases) < 0) {
        commit_list_free(bases);
        commit_list_free(*result);
        *result = NULL;
        return -1;
      }
      if (!new_commits)
        new_commits = bases;
      else
        end->next = bases;
      for (k = bases; k; k = k->next)
        end = k;
    }
    commit_list_free(*result);
    *result = new_commits;
  }
  return 0;
}

static int remove_redundant_no_gen(struct repository *r,
           struct commit **array,
           size_t cnt, size_t *dedup_cnt)
{
  struct commit **work;
  unsigned char *redundant;
  size_t *filled_index;
  size_t i, j, filled;

  CALLOC_ARRAY(work, cnt);
  redundant = xcalloc(cnt, 1);
  ALLOC_ARRAY(filled_index, cnt - 1);

  for (i = 0; i < cnt; i++)
    repo_parse_commit(r, array[i]);
  for (i = 0; i < cnt; i++) {
    struct commit_list *common = NULL;
    timestamp_t min_generation = commit_graph_generation(array[i]);

    if (redundant[i])
      continue;
    for (j = filled = 0; j < cnt; j++) {
      timestamp_t curr_generation;
      if (i == j || redundant[j])
        continue;
      filled_index[filled] = j;
      work[filled++] = array[j];

      curr_generation = commit_graph_generation(array[j]);
      if (curr_generation < min_generation)
        min_generation = curr_generation;
    }
    if (paint_down_to_common(r, array[i], filled,
           work, min_generation,
           MERGE_BASE_FIND_ALL, &common)) {
      clear_commit_marks(array[i], all_flags);
      clear_commit_marks_many(filled, work, all_flags);
      commit_list_free(common);
      free(work);
      free(redundant);
      free(filled_index);
      return -1;
    }
    if (array[i]->object.flags & PARENT2)
      redundant[i] = 1;
    for (j = 0; j < filled; j++)
      if (work[j]->object.flags & PARENT1)
        redundant[filled_index[j]] = 1;
    clear_commit_marks(array[i], all_flags);
    clear_commit_marks_many(filled, work, all_flags);
    commit_list_free(common);
  }

  /* Now collect the result */
  COPY_ARRAY(work, array, cnt);
  for (i = filled = 0; i < cnt; i++)
    if (!redundant[i])
      array[filled++] = work[i];
  *dedup_cnt = filled;
  free(work);
  free(redundant);
  free(filled_index);
  return 0;
}

static int remove_redundant_with_gen(struct repository *r,
             struct commit **array, size_t cnt,
             size_t *dedup_cnt)
{
  size_t i, count_non_stale = 0, count_still_independent = cnt;
  timestamp_t min_generation = GENERATION_NUMBER_INFINITY;
  struct commit **sorted;
  struct commit_stack walk_start = COMMIT_STACK_INIT;
  size_t min_gen_pos = 0;

  /*
   * Sort the input by generation number, ascending. This allows
   * us to increase the "min_generation" limit when we discover
   * the commit with lowest generation is STALE. The index
   * min_gen_pos points to the current position within 'array'
   * that is not yet known to be STALE.
   */
  DUP_ARRAY(sorted, array, cnt);
  QSORT(sorted, cnt, compare_commits_by_gen);
  min_generation = commit_graph_generation(sorted[0]);

  commit_stack_grow(&walk_start, cnt);

  /* Mark all parents of the input as STALE */
  for (i = 0; i < cnt; i++) {
    struct commit_list *parents;

    repo_parse_commit(r, array[i]);
    array[i]->object.flags |= RESULT;
    parents = array[i]->parents;

    while (parents) {
      repo_parse_commit(r, parents->item);
      if (!(parents->item->object.flags & STALE)) {
        parents->item->object.flags |= STALE;
        commit_stack_push(&walk_start, parents->item);
      }
      parents = parents->next;
    }
  }

  QSORT(walk_start.items, walk_start.nr, compare_commits_by_gen);

  /* remove STALE bit for now to allow walking through parents */
  for (i = 0; i < walk_start.nr; i++)
    walk_start.items[i]->object.flags &= ~STALE;

  /*
   * Start walking from the highest generation. Hopefully, it will
   * find all other items during the first-parent walk, and we can
   * terminate early. Otherwise, we will do the same amount of work
   * as before.
   */
  for (i = walk_start.nr; i && count_still_independent > 1; i--) {
    /* push the STALE bits up to min generation */
    struct commit_list *stack = NULL;

    commit_list_insert(walk_start.items[i - 1], &stack);
    walk_start.items[i - 1]->object.flags |= STALE;

    while (stack) {
      struct commit_list *parents;
      struct commit *c = stack->item;

      repo_parse_commit(r, c);

      if (c->object.flags & RESULT) {
        c->object.flags &= ~RESULT;
        if (--count_still_independent <= 1)
          break;
        if (oideq(&c->object.oid, &sorted[min_gen_pos]->object.oid)) {
          while (min_gen_pos < cnt - 1 &&
                 (sorted[min_gen_pos]->object.flags & STALE))
            min_gen_pos++;
          min_generation = commit_graph_generation(sorted[min_gen_pos]);
        }
      }

      if (commit_graph_generation(c) < min_generation) {
        pop_commit(&stack);
        continue;
      }

      parents = c->parents;
      while (parents) {
        if (!(parents->item->object.flags & STALE)) {
          parents->item->object.flags |= STALE;
          commit_list_insert(parents->item, &stack);
          break;
        }
        parents = parents->next;
      }

      /* pop if all parents have been visited already */
      if (!parents)
        pop_commit(&stack);
    }
    commit_list_free(stack);
  }
  free(sorted);

  /* clear result */
  for (i = 0; i < cnt; i++)
    array[i]->object.flags &= ~RESULT;

  /* rearrange array */
  for (i = count_non_stale = 0; i < cnt; i++) {
    if (!(array[i]->object.flags & STALE))
      array[count_non_stale++] = array[i];
  }

  /* clear marks */
  clear_commit_marks_many(walk_start.nr, walk_start.items, STALE);
  commit_stack_clear(&walk_start);

  *dedup_cnt = count_non_stale;
  return 0;
}

static int remove_redundant(struct repository *r, struct commit **array,
          size_t cnt, size_t *dedup_cnt)
{
  /*
   * Some commit in the array may be an ancestor of
   * another commit.  Move the independent commits to the
   * beginning of 'array' and return their number. Callers
   * should not rely upon the contents of 'array' after
   * that number.
   */
  if (generation_numbers_enabled(r)) {
    /*
     * If we have a single commit with finite generation
     * number, then the _with_gen algorithm is preferred.
     */
    for (size_t i = 0; i < cnt; i++) {
      if (commit_graph_generation(array[i]) < GENERATION_NUMBER_INFINITY)
        return remove_redundant_with_gen(r, array, cnt, dedup_cnt);
    }
  }

  return remove_redundant_no_gen(r, array, cnt, dedup_cnt);
}

static int get_merge_bases_many_0(struct repository *r,
          struct commit *one,
          size_t n,
          struct commit **twos,
          int cleanup,
          enum merge_base_flags mb_flags,
          struct commit_list **result)
{
  struct commit_list *list, **tail = result;
  struct commit **rslt;
  size_t cnt, i;
  int ret;

  if (merge_bases_many(r, one, n, twos, mb_flags, result) < 0)
    return -1;
  for (i = 0; i < n; i++) {
    if (one == twos[i])
      return 0;
  }
  if (!*result || !(*result)->next) {
    if (cleanup) {
      clear_commit_marks(one, all_flags);
      clear_commit_marks_many(n, twos, all_flags);
    }
    return 0;
  }

  /* There are more than one */
  cnt = commit_list_count(*result);
  CALLOC_ARRAY(rslt, cnt);
  for (list = *result, i = 0; list; list = list->next)
    rslt[i++] = list->item;
  commit_list_free(*result);
  *result = NULL;

  clear_commit_marks(one, all_flags);
  clear_commit_marks_many(n, twos, all_flags);

  ret = remove_redundant(r, rslt, cnt, &cnt);
  if (ret < 0) {
    free(rslt);
    return -1;
  }
  for (i = 0; i < cnt; i++)
    tail = commit_list_append(rslt[i], tail);
  commit_list_sort_by_date(result);
  free(rslt);
  return 0;
}

int repo_get_merge_bases_many(struct repository *r,
            struct commit *one,
            size_t n,
            struct commit **twos,
            struct commit_list **result)
{
  return get_merge_bases_many_0(r, one, n, twos, 1,
             MERGE_BASE_FIND_ALL, result);
}

int repo_get_merge_bases_many_dirty(struct repository *r,
            struct commit *one,
            size_t n,
            struct commit **twos,
            enum merge_base_flags mb_flags,
            struct commit_list **result)
{
  return get_merge_bases_many_0(r, one, n, twos, 0, mb_flags, result);
}

int repo_get_merge_bases(struct repository *r,
       struct commit *one,
       struct commit *two,
       struct commit_list **result)
{
  return get_merge_bases_many_0(r, one, 1, &two, 1,
             MERGE_BASE_FIND_ALL, result);
}

/*
 * Is "commit" a descendant of one of the elements on the "with_commit" list?
 */
int repo_is_descendant_of(struct repository *r,
        struct commit *commit,
        struct commit_list *with_commit)
{
  if (!with_commit)
    return 1;

  if (generation_numbers_enabled(r)) {
    struct commit_list *from_list = NULL;
    int result;
    commit_list_insert(commit, &from_list);
    result = can_all_from_reach(r, from_list, with_commit, 0);
    commit_list_free(from_list);
    return result;
  } else {
    while (with_commit) {
      struct commit *other;
      int ret;

      other = with_commit->item;
      with_commit = with_commit->next;
      ret = repo_in_merge_bases_many(r, other, 1, &commit, 0);
      if (ret)
        return ret;
    }
    return 0;
  }
}

/*
 * Is "commit" an ancestor of one of the "references"?
 */
int repo_in_merge_bases_many(struct repository *r, struct commit *commit,
           int nr_reference, struct commit **reference,
           int ignore_missing_commits)
{
  struct commit_list *bases = NULL;
  int ret = 0, i;
  timestamp_t generation, max_generation = GENERATION_NUMBER_ZERO;
  enum merge_base_flags mb_flags = MERGE_BASE_FIND_ALL;

  if (ignore_missing_commits)
    mb_flags |= MERGE_BASE_IGNORE_MISSING_COMMITS;

  if (repo_parse_commit(r, commit))
    return ignore_missing_commits ? 0 : -1;
  for (i = 0; i < nr_reference; i++) {
    if (repo_parse_commit(r, reference[i]))
      return ignore_missing_commits ? 0 : -1;

    generation = commit_graph_generation(reference[i]);
    if (generation > max_generation)
      max_generation = generation;
  }

  generation = commit_graph_generation(commit);
  if (generation > max_generation)
    return ret;

  if (paint_down_to_common(r, commit,
         nr_reference, reference,
         generation, mb_flags, &bases))
    ret = -1;
  else if (commit->object.flags & PARENT2)
    ret = 1;
  clear_commit_marks(commit, all_flags);
  clear_commit_marks_many(nr_reference, reference, all_flags);
  commit_list_free(bases);
  return ret;
}

/*
 * Is "commit" an ancestor of (i.e. reachable from) the "reference"?
 */
int repo_in_merge_bases(struct repository *r,
      struct commit *commit,
      struct commit *reference)
{
  int res;
  struct commit_list *list = NULL;
  struct commit_list **next = &list;

  next = commit_list_append(commit, next);
  res = repo_is_descendant_of(r, reference, list);
  commit_list_free(list);

  return res;
}

struct commit_list *reduce_heads(struct commit_list *heads)
{
  struct commit_list *p;
  struct commit_list *result = NULL, **tail = &result;
  struct commit **array;
  size_t num_head, i;
  int ret;

  if (!heads)
    return NULL;

  /* Uniquify */
  for (p = heads; p; p = p->next)
    p->item->object.flags &= ~STALE;
  for (p = heads, num_head = 0; p; p = p->next) {
    if (p->item->object.flags & STALE)
      continue;
    p->item->object.flags |= STALE;
    num_head++;
  }
  CALLOC_ARRAY(array, num_head);
  for (p = heads, i = 0; p; p = p->next) {
    if (p->item->object.flags & STALE) {
      array[i++] = p->item;
      p->item->object.flags &= ~STALE;
    }
  }

  ret = remove_redundant(the_repository, array, num_head, &num_head);
  if (ret < 0) {
    free(array);
    return NULL;
  }

  for (i = 0; i < num_head; i++)
    tail = &commit_list_insert(array[i], tail)->next;
  free(array);
  return result;
}

void reduce_heads_replace(struct commit_list **heads)
{
  struct commit_list *result = reduce_heads(*heads);
  commit_list_free(*heads);
  *heads = result;
}

int ref_newer(const struct object_id *new_oid, const struct object_id *old_oid)
{
  struct object *o;
  struct commit *old_commit, *new_commit;
  struct commit_list *old_commit_list = NULL;
  int ret;

  /*
   * Both new_commit and old_commit must be commit-ish and new_commit is descendant of
   * old_commit.  Otherwise we require --force.
   */
  o = deref_tag(the_repository, parse_object(the_repository, old_oid),
          NULL, 0);
  if (!o || o->type != OBJ_COMMIT)
    return 0;
  old_commit = (struct commit *) o;

  o = deref_tag(the_repository, parse_object(the_repository, new_oid),
          NULL, 0);
  if (!o || o->type != OBJ_COMMIT)
    return 0;
  new_commit = (struct commit *) o;

  if (repo_parse_commit(the_repository, new_commit) < 0)
    return 0;

  commit_list_insert(old_commit, &old_commit_list);
  ret = repo_is_descendant_of(the_repository,
            new_commit, old_commit_list);
  if (ret < 0)
    exit(128);
  commit_list_free(old_commit_list);
  return ret;
}

/*
 * Mimicking the real stack, this stack lives on the heap, avoiding stack
 * overflows.
 *
 * At each recursion step, the stack items points to the commits whose
 * ancestors are to be inspected.
 */
struct contains_stack {
  int nr, alloc;
  struct contains_stack_entry {
    struct commit *commit;
    struct commit_list *parents;
  } *contains_stack;
};

static int in_commit_list(const struct commit_list *want, struct commit *c)
{
  for (; want; want = want->next)
    if (oideq(&want->item->object.oid, &c->object.oid))
      return 1;
  return 0;
}

/*
 * Test whether the candidate is contained in the list.
 * Do not recurse to find out, though, but return CONTAINS_UNKNOWN if
 * inconclusive.
 */
static enum contains_result contains_test(struct commit *candidate,
            const struct commit_list *want,
            struct contains_cache *cache,
            timestamp_t cutoff)
{
  enum contains_result *cached = contains_cache_at(cache, candidate);

  /* If we already have the answer cached, return that. */
  if (*cached)
    return *cached;

  /* or are we it? */
  if (in_commit_list(want, candidate)) {
    *cached = CONTAINS_YES;
    return CONTAINS_YES;
  }

  /* Otherwise, we don't know; prepare to recurse */
  parse_commit_or_die(candidate);

  if (commit_graph_generation(candidate) < cutoff)
    return CONTAINS_NO;

  return CONTAINS_UNKNOWN;
}

static void push_to_contains_stack(struct commit *candidate, struct contains_stack *contains_stack)
{
  ALLOC_GROW(contains_stack->contains_stack, contains_stack->nr + 1, contains_stack->alloc);
  contains_stack->contains_stack[contains_stack->nr].commit = candidate;
  contains_stack->contains_stack[contains_stack->nr++].parents = candidate->parents;
}

static enum contains_result contains_tag_algo(struct commit *candidate,
                const struct commit_list *want,
                struct contains_cache *cache)
{
  struct contains_stack contains_stack = { 0, 0, NULL };
  enum contains_result result;
  timestamp_t cutoff = GENERATION_NUMBER_INFINITY;
  const struct commit_list *p;

  for (p = want; p; p = p->next) {
    timestamp_t generation;
    struct commit *c = p->item;
    load_commit_graph_info(the_repository, c);
    generation = commit_graph_generation(c);
    if (generation < cutoff)
      cutoff = generation;
  }

  result = contains_test(candidate, want, cache, cutoff);
  if (result != CONTAINS_UNKNOWN)
    return result;

  *contains_cache_at(cache, candidate) = CONTAINS_IN_PROGRESS;
  push_to_contains_stack(candidate, &contains_stack);
  while (contains_stack.nr) {
    struct contains_stack_entry *entry = &contains_stack.contains_stack[contains_stack.nr - 1];
    struct commit *commit = entry->commit;
    struct commit_list *parents = entry->parents;

    if (!parents) {
      *contains_cache_at(cache, commit) = CONTAINS_NO;
      contains_stack.nr--;
    }
    /*
     * A parent may have just been popped and marked, or may still
     * be active when replacement refs create a cycle.
     */
    else switch (contains_test(parents->item, want, cache, cutoff)) {
    case CONTAINS_YES:
      *contains_cache_at(cache, commit) = CONTAINS_YES;
      contains_stack.nr--;
      break;
    case CONTAINS_NO:
      entry->parents = parents->next;
      break;
    case CONTAINS_IN_PROGRESS:
      die(_("commit ancestry contains a cycle"));
    case CONTAINS_UNKNOWN:
      *contains_cache_at(cache, parents->item) =
        CONTAINS_IN_PROGRESS;
      push_to_contains_stack(parents->item, &contains_stack);
      break;
    }
  }
  free(contains_stack.contains_stack);
  return contains_test(candidate, want, cache, cutoff);
}

int commit_contains(struct ref_filter *filter, struct commit *commit,
        struct commit_list *list, struct contains_cache *cache)
{
  int result;

  if (filter->with_commit_tag_algo ||
      generation_numbers_enabled(the_repository))
    return contains_tag_algo(commit, list, cache) == CONTAINS_YES;

  result = repo_is_descendant_of(the_repository, commit, list);
  if (result < 0)
    die(_("failed to check reachability"));
  return result;
}

int can_all_from_reach_with_flag(struct repository *r,
         struct object_array *from,
         unsigned int with_flag,
         unsigned int assign_flag,
         timestamp_t min_commit_date,
         timestamp_t min_generation)
{
  struct commit **list = NULL;
  size_t i;
  size_t nr_commits;
  int result = 1;

  ALLOC_ARRAY(list, from->nr);
  nr_commits = 0;
  for (i = 0; i < from->nr; i++) {
    struct object *from_one = from->objects[i].item;

    if (!from_one || from_one->flags & assign_flag)
      continue;

    from_one = deref_tag(r, from_one, "a from object", 0);
    if (!from_one || from_one->type != OBJ_COMMIT) {
      /*
       * no way to tell if this is reachable by
       * looking at the ancestry chain alone, so
       * leave a note to ourselves not to worry about
       * this object anymore.
       */
      from->objects[i].item->flags |= assign_flag;
      continue;
    }

    list[nr_commits] = (struct commit *)from_one;
    if (repo_parse_commit(r, list[nr_commits]) ||
        commit_graph_generation(list[nr_commits]) < min_generation) {
      result = 0;
      goto cleanup;
    }

    nr_commits++;
  }

  QSORT(list, nr_commits, compare_commits_by_gen);

  for (i = 0; i < nr_commits; i++) {
    /* DFS from list[i] */
    struct commit_list *stack = NULL;

    list[i]->object.flags |= assign_flag;
    commit_list_insert(list[i], &stack);

    while (stack) {
      struct commit_list *parent;

      if (stack->item->object.flags & (with_flag | RESULT)) {
        pop_commit(&stack);
        if (stack)
          stack->item->object.flags |= RESULT;
        continue;
      }

      for (parent = stack->item->parents; parent; parent = parent->next) {
        if (parent->item->object.flags & (with_flag | RESULT))
          stack->item->object.flags |= RESULT;

        if (!(parent->item->object.flags & assign_flag)) {
          parent->item->object.flags |= assign_flag;

          if (repo_parse_commit(r, parent->item) ||
              parent->item->date < min_commit_date ||
              commit_graph_generation(parent->item) < min_generation)
            continue;

          commit_list_insert(parent->item, &stack);
          break;
        }
      }

      if (!parent)
        pop_commit(&stack);
    }

    if (!(list[i]->object.flags & (with_flag | RESULT))) {
      result = 0;
      goto cleanup;
    }
  }

cleanup:
  clear_commit_marks_many(nr_commits, list, RESULT | assign_flag);
  free(list);

  for (i = 0; i < from->nr; i++) {
    struct object *from_one = from->objects[i].item;

    if (from_one)
      from_one->flags &= ~assign_flag;
  }

  return result;
}

int can_all_from_reach(struct repository *r, struct commit_list *from,
           struct commit_list *to, int cutoff_by_min_date)
{
  struct object_array from_objs = OBJECT_ARRAY_INIT;
  struct commit_list *from_iter = from, *to_iter = to;
  int result;
  timestamp_t min_commit_date = cutoff_by_min_date ? from->item->date : 0;
  timestamp_t min_generation = GENERATION_NUMBER_INFINITY;

  while (from_iter) {
    add_object_array(&from_iter->item->object, NULL, &from_objs);

    if (!repo_parse_commit(r, from_iter->item)) {
      timestamp_t generation;
      if (from_iter->item->date < min_commit_date)
        min_commit_date = from_iter->item->date;

      generation = commit_graph_generation(from_iter->item);
      if (generation < min_generation)
        min_generation = generation;
    }

    from_iter = from_iter->next;
  }

  while (to_iter) {
    if (!repo_parse_commit(r, to_iter->item)) {
      timestamp_t generation;
      if (to_iter->item->date < min_commit_date)
        min_commit_date = to_iter->item->date;

      generation = commit_graph_generation(to_iter->item);
      if (generation < min_generation)
        min_generation = generation;
    }

    to_iter->item->object.flags |= PARENT2;

    to_iter = to_iter->next;
  }

  result = can_all_from_reach_with_flag(r, &from_objs, PARENT2, PARENT1,
                min_commit_date, min_generation);

  while (from) {
    clear_commit_marks(from->item, PARENT1);
    from = from->next;
  }

  while (to) {
    clear_commit_marks(to->item, PARENT2);
    to = to->next;
  }

  object_array_clear(&from_objs);
  return result;
}

struct commit_list *get_reachable_subset(struct commit **from, size_t nr_from,
           struct commit **to, size_t nr_to,
           unsigned int reachable_flag)
{
  struct commit **item;
  struct commit *current;
  struct commit_list *found_commits = NULL;
  struct commit **to_last = to + nr_to;
  struct commit **from_last = from + nr_from;
  timestamp_t min_generation = GENERATION_NUMBER_INFINITY;
  int num_to_find = 0;

  struct prio_queue queue = { compare_commits_by_gen_then_commit_date };

  for (item = to; item < to_last; item++) {
    timestamp_t generation;
    struct commit *c = *item;

    repo_parse_commit(the_repository, c);
    generation = commit_graph_generation(c);
    if (generation < min_generation)
      min_generation = generation;

    if (!(c->object.flags & PARENT1)) {
      c->object.flags |= PARENT1;
      num_to_find++;
    }
  }

  for (item = from; item < from_last; item++) {
    struct commit *c = *item;
    if (!(c->object.flags & PARENT2)) {
      c->object.flags |= PARENT2;
      repo_parse_commit(the_repository, c);

      prio_queue_put(&queue, *item);
    }
  }

  while (num_to_find && (current = prio_queue_get(&queue)) != NULL) {
    struct commit_list *parents;

    if (current->object.flags & PARENT1) {
      current->object.flags &= ~PARENT1;
      current->object.flags |= reachable_flag;
      commit_list_insert(current, &found_commits);
      num_to_find--;
    }

    for (parents = current->parents; parents; parents = parents->next) {
      struct commit *p = parents->item;

      repo_parse_commit(the_repository, p);

      if (commit_graph_generation(p) < min_generation)
        continue;

      if (p->object.flags & PARENT2)
        continue;

      p->object.flags |= PARENT2;
      prio_queue_put(&queue, p);
    }
  }

  clear_prio_queue(&queue);

  clear_commit_marks_many(nr_to, to, PARENT1);
  clear_commit_marks_many(nr_from, from, PARENT2);

  return found_commits;
}

define_commit_slab(bit_arrays, struct bitmap *);
static struct bit_arrays bit_arrays;

static void insert_no_dup(struct nonstale_queue *queue, struct commit *c)
{
  if (c->object.flags & PARENT2)
    return;
  nonstale_queue_put(queue, c);
  c->object.flags |= PARENT2;
}

static struct bitmap *get_bit_array(struct commit *c, int width)
{
  struct bitmap **bitmap = bit_arrays_at(&bit_arrays, c);
  if (!*bitmap)
    *bitmap = bitmap_word_alloc(width);
  return *bitmap;
}

static void free_bit_array(struct commit *c)
{
  struct bitmap **bitmap = bit_arrays_at(&bit_arrays, c);
  if (!*bitmap)
    return;
  bitmap_free(*bitmap);
  *bitmap = NULL;
}

void ahead_behind(struct repository *r,
      struct commit **commits, size_t commits_nr,
      struct ahead_behind_count *counts, size_t counts_nr)
{
  struct nonstale_queue queue = {
    { .compare = compare_commits_by_gen_then_commit_date }
  };
  void *entry;
  size_t width = DIV_ROUND_UP(commits_nr, BITS_IN_EWORD);

  if (!commits_nr || !counts_nr)
    return;

  for (size_t i = 0; i < counts_nr; i++) {
    counts[i].ahead = 0;
    counts[i].behind = 0;
  }

  ensure_generations_valid(r, commits, commits_nr);

  init_bit_arrays(&bit_arrays);

  for (size_t i = 0; i < commits_nr; i++) {
    struct commit *c = commits[i];
    struct bitmap *bitmap = get_bit_array(c, width);

    bitmap_set(bitmap, i);
    insert_no_dup(&queue, c);
  }

  while (queue.max_nonstale) {
    struct commit *c = nonstale_queue_get(&queue);
    struct commit_list *p;
    struct bitmap *bitmap_c = get_bit_array(c, width);

    for (size_t i = 0; i < counts_nr; i++) {
      int reach_from_tip = !!bitmap_get(bitmap_c, counts[i].tip_index);
      int reach_from_base = !!bitmap_get(bitmap_c, counts[i].base_index);

      if (reach_from_tip ^ reach_from_base) {
        if (reach_from_base)
          counts[i].behind++;
        else
          counts[i].ahead++;
      }
    }

    for (p = c->parents; p; p = p->next) {
      struct bitmap *bitmap_p;

      repo_parse_commit(r, p->item);

      bitmap_p = get_bit_array(p->item, width);
      bitmap_or(bitmap_p, bitmap_c);

      /*
       * If this parent is reachable from every starting
       * commit, then none of its ancestors can contribute
       * to the ahead/behind count. Mark it as STALE, so
       * we can stop the walk when every commit in the
       * queue is STALE.
       */
      if (bitmap_popcount(bitmap_p) == commits_nr)
        p->item->object.flags |= STALE;

      insert_no_dup(&queue, p->item);
    }

    free_bit_array(c);
  }

  /* STALE is used here, PARENT2 is used by insert_no_dup(). */
  repo_clear_commit_marks(r, PARENT2 | STALE);
  prio_queue_for_each(&queue.pq, entry)
    free_bit_array(entry);
  clear_bit_arrays(&bit_arrays);
  clear_nonstale_queue(&queue);
}

struct commit_and_index {
  struct commit *commit;
  timestamp_t generation;
};

static int compare_commit_and_index_by_generation(const void *va, const void *vb)
{
  const struct commit_and_index *a = (const struct commit_and_index *)va;
  const struct commit_and_index *b = (const struct commit_and_index *)vb;

  if (a->generation > b->generation)
    return 1;
  if (a->generation < b->generation)
    return -1;
  return 0;
}

void tips_reachable_from_bases(struct repository *r,
             struct commit_list *bases,
             struct commit **tips, size_t tips_nr,
             int mark)
{
  struct commit_and_index *commits;
  size_t min_generation_index = 0;
  timestamp_t min_generation;
  struct commit_list *stack = NULL;

  if (!bases || !tips || !tips_nr)
    return;

  /*
   * Do a depth-first search starting at 'bases' to search for the
   * tips. Stop at the lowest (un-found) generation number. When
   * finding the lowest commit, increase the minimum generation
   * number to the next lowest (un-found) generation number.
   */

  CALLOC_ARRAY(commits, tips_nr);

  for (size_t i = 0; i < tips_nr; i++) {
    commits[i].commit = tips[i];
    commits[i].generation = commit_graph_generation(tips[i]);
  }

  /* Sort with generation number ascending. */
  QSORT(commits, tips_nr, compare_commit_and_index_by_generation);
  min_generation = commits[0].generation;

  for (size_t i = 0; i < tips_nr; i++)
    commits[i].commit->object.flags |= RESULT;

  while (bases) {
    repo_parse_commit(r, bases->item);
    commit_list_insert(bases->item, &stack);
    bases = bases->next;
  }

  while (stack) {
    int explored_all_parents = 1;
    struct commit_list *p;
    struct commit *c = stack->item;

    /* Does it match any of our tips? */
    {
      if (c->object.flags & RESULT) {
        c->object.flags |= mark;

        if (commits[min_generation_index].commit->object.flags & mark) {
          unsigned int k = min_generation_index + 1;
          while (k < tips_nr &&
                 (commits[k].commit->object.flags & mark))
            k++;

          /* Terminate early if all found. */
          if (k >= tips_nr)
            goto done;

          min_generation_index = k;
          min_generation = commits[k].generation;
        }
      }
    }

    for (p = c->parents; p; p = p->next) {
      repo_parse_commit(r, p->item);

      /* Have we already explored this parent? */
      if (p->item->object.flags & SEEN)
        continue;

      /* Is it below the current minimum generation? */
      if (commit_graph_generation(p->item) < min_generation)
        continue;

      /* Ok, we will explore from here on. */
      p->item->object.flags |= SEEN;
      explored_all_parents = 0;
      commit_list_insert(p->item, &stack);
      break;
    }

    if (explored_all_parents)
      pop_commit(&stack);
  }

done:
  for (size_t i = 0; i < tips_nr; i++)
    commits[i].commit->object.flags &= ~RESULT;
  free(commits);
  repo_clear_commit_marks(r, SEEN);
  commit_list_free(stack);
}

/*
 * This slab initializes integers to zero, so use "-1" for "tip is best" and
 * "i + 1" for "bases[i] is best".
 */
define_commit_slab(best_branch_base, int);
static struct best_branch_base best_branch_base;
#define get_best(c) (*best_branch_base_at(&best_branch_base, (c)))
#define set_best(c,v) (*best_branch_base_at(&best_branch_base, (c)) = (v))

int get_branch_base_for_tip(struct repository *r,
          struct commit *tip,
          struct commit **bases,
          size_t bases_nr)
{
  int best_index = -1;
  struct commit *c, *branch_point = NULL;
  struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
  int found_missing_gen = 0;

  if (!bases_nr)
    return -1;

  repo_parse_commit(r, tip);
  if (commit_graph_generation(tip) == GENERATION_NUMBER_INFINITY)
    found_missing_gen = 1;

  /* Check for missing generation numbers. */
  for (size_t i = 0; i < bases_nr; i++) {
    struct commit *c = bases[i];
    repo_parse_commit(r, c);
    if (commit_graph_generation(c) == GENERATION_NUMBER_INFINITY)
      found_missing_gen = 1;
  }

  if (found_missing_gen) {
    struct commit **commits;
    size_t commits_nr = bases_nr + 1;

    CALLOC_ARRAY(commits, commits_nr);
    COPY_ARRAY(commits, bases, bases_nr);
    commits[bases_nr] = tip;
    ensure_generations_valid(r, commits, commits_nr);
    free(commits);
  }

  /* Initialize queue and slab now that generations are guaranteed. */
  init_best_branch_base(&best_branch_base);
  set_best(tip, -1);
  prio_queue_put(&queue, tip);

  for (size_t i = 0; i < bases_nr; i++) {
    struct commit *c = bases[i];
    int best = get_best(c);

    /* Has this already been marked as best by another commit? */
    if (best) {
      if (best == -1) {
        /* We agree at this position. Stop now. */
        best_index = i + 1;
        goto cleanup;
      }
      continue;
    }

    set_best(c, i + 1);
    prio_queue_put(&queue, c);
  }

  while ((c = prio_queue_get(&queue))) {
    int best_for_c = get_best(c);
    int best_for_p, positive;
    struct commit *parent;

    /* Have we reached a known branch point? It's optimal. */
    if (c == branch_point)
      break;

    repo_parse_commit(r, c);
    if (!c->parents)
      continue;

    parent = c->parents->item;
    repo_parse_commit(r, parent);
    best_for_p = get_best(parent);

    if (!best_for_p) {
      /* 'parent' is new, so pass along best_for_c. */
      set_best(parent, best_for_c);
      prio_queue_put(&queue, parent);
      continue;
    }

    if (best_for_p > 0 && best_for_c > 0) {
      /* Collision among bases. Minimize. */
      if (best_for_c < best_for_p)
        set_best(parent, best_for_c);
      continue;
    }

    /*
     * At this point, we have reached a commit that is reachable
     * from the tip, either from 'c' or from an earlier commit to
     * have 'parent' as its first parent.
     *
     * Update 'best_index' to match the minimum of all base indices
     * to reach 'parent'.
     */

    /* Exactly one is positive due to initial conditions. */
    positive = (best_for_c < 0) ? best_for_p : best_for_c;

    if (best_index < 0 || positive < best_index)
      best_index = positive;

    /* No matter what, track that the parent is reachable from tip. */
    set_best(parent, -1);
    branch_point = parent;
  }

cleanup:
  clear_best_branch_base(&best_branch_base);
  clear_prio_queue(&queue);
  return best_index > 0 ? best_index - 1 : -1;
}

Coverage Report

Created: 2026-10-17 07:15